Why crocodiles have changed so little since the age of the dinosaurs

 New research by scientists at the University of Bristol explains how a 'stop-start' pattern of evolution, governed by environmental change, could explain why crocodiles have changed so little since the age of the dinosaurs.

Crocodiles today look very similar to ones from the Jurassic period some 200 million years ago. There are also very few species alive today -- just 25. Other animals such as lizards and birds have achieved a diversity of many thousands of species in the same amount of time or less.

Prehistory also saw types of crocodile we don't see today, including giants as big as dinosaurs, plant-eaters, fast runners and serpentine forms that lived in the sea.

In the new research, published today in the journal Nature Communications Biology, the scientists explain how crocodiles follow a pattern of evolution known as 'punctuated equilibrium'.

The rate of their evolution is generally slow, but occasionally they evolve more quickly because the environment has changed. In particular, this new research suggests that their evolution speeds up when the climate is warmer, and that their body size increases.

Lead author Dr Max Stockdale from the University of Bristol's School of Geographical Sciences, said: "Our analysis used a machine learning algorithm to estimate rates of evolution. Evolutionary rate is the amount of change that has taken place over a given amount of time, which we can work out by comparing measurements from fossils and taking into account how old they are.

"For our study we measured body size, which is important because it interacts with how fast animals grow, how much food they need, how big their populations are and how likely they are to become extinct."

The findings show that the limited diversity of crocodiles and their apparent lack of evolution is a result of a slow evolutionary rate. It seems the crocodiles arrived at a body plan that was very efficient and versatile enough that they didn't need to change it in order to survive.

This versatility could be one explanation why crocodiles survived the meteor impact at the end of the Cretaceous period, in which the dinosaurs perished. Crocodiles generally thrive better in warm conditions because they cannot control their body temperature and require warmth from the environment.

The climate during the age of dinosaurs was warmer than it is today, and that may explain why there were many more varieties of crocodile than we see now. Being able to draw energy from the sun means they do not need to eat as much as a warm-blooded animal like a bird or a mammal.

Dr Stockdale added: "It is fascinating to see how intricate a relationship exists between the earth and the living things we share it with. The crocodiles landed upon a lifestyle that was versatile enough to adapt to the enormous environmental changes that have taken place since the dinosaurs were around."

Read more at Science Daily

Oldest hominins of Olduvai Gorge persisted across changing environments

 Olduvai (now Oldupai) Gorge, known as the Cradle of Humankind, is a UNESCO World Heritage site in Tanzania, made famous by Louis and Mary Leakey. New interdisciplinary field work has led to the discovery of the oldest archaeological site in Oldupai Gorge as reported in Nature Communications, which shows that early human used a wide diversity of habitats amidst environmental changes across a 200,000 year-long period.

Located in the heart of eastern Africa, the Rift System is a prime region for human origins research, boasting extraordinary records of extinct human species and environmental records spanning several million years. For more than a century, archaeologists and human palaeontologists have been exploring the East African Rift outcrops and unearthing hominin fossils in surveys and excavations. However, understanding of the environmental contexts in which these hominins lived has remained elusive due to a dearth of ecological studies in direct association with the cultural remains.

In the new study, published in Nature Communications, researchers from the Max Planck Institute for for the Science of Human History teamed up with lead partners from the University of Calgary, Canada, and the University of Dar es Salaam, Tanzania, to excavate the site of 'Ewass Oldupa' (meaning on 'the way to the Gorge' in the local Maa language, as the site straddles the path that links the canyon's rim with its bottom). The excavations uncovered the oldest Oldowan stone tools ever found at Oldupai Gorge, dating to ~2 million years ago. Excavations in long sequences of stratified sediments and dated volcanic horizons indicated hominin presence at Ewass Oldupai from 2.0 to 1.8 million years ago.

Fossils of mammals (wild cattle and pigs, hippos, panthers, lions, hyena, primates), reptiles and birds, together with a range of multidisciplinary scientific studies, revealed habitat changes over 200,000 years in riverine and lake systems, including fern meadows, woodland mosaics, naturally burned landscapes, lakeside palm groves and dry steppe habitats. The uncovered evidence shows periodic but recurrent land use across a subset of environments, punctuated with times when there is an absence of hominin activity.

Dr. Pastory Bushozi of Dar es Salaam University, Tanzania, notes, "the occupation of varied and unstable environments, including after volcanic activity, is one of the earliest examples of adaptation to major ecological transformations."

Hominin occupation of fluctuating and disturbed environments is unique for this early time period and shows complex behavioural adaptations among early human groups. In the face of changing habitats, early humans did not substantially alter their toolkits, but instead their technology remained stable over time. Indicative of their versatility, typical Oldowan stone tools, consisting of pebble and cobble cores and sharp-edged flakes and polyhedral cobbles, continued to be used even as habitats changed. The implication is that by two million years ago, early humans had the behavioural capacity to continually and consistently exploit a multitude of habitats, using reliable stone toolkits, to likely process plants and butcher animals over the long term.

Read more at Science Daily

Delivering the news with humor makes young adults more likely to remember and share

 In the early decades of televised news, Americans turned to the stern faces of newsmen like Walter Cronkite, Tom Brokaw, and Dan Rather as trusted sources for news of the important events in America and around the world, delivered with gravitas and measured voices. The rise of comedy-news programs, helmed by the likes of Jon Stewart, Stephen Colbert, John Oliver, Trevor Noah, and Samantha Bee, raised concerns over the blending of entertainment and news. But could the merging of humor and news actually help inform the public?

In fact, new research suggests that humor may help keep people informed about politics. A study from the Annenberg School for Communication at the University of Pennsylvania and the School of Communication at Ohio State University found that, when compared to non-humorous news clips, viewers are not only more likely to share humorously presented news but are also more likely to remember the content from these segments.

"For democracy to work, it is really important for people to engage with news and politics and to be informed about public affairs," says senior author Emily Falk, Professor of Communication, Psychology, and Marketing at Annenberg. "We wanted to test whether humor might make news more socially relevant, and therefore motivate people to remember it and share it."

The researchers recruited young adults (18-34 years old) to watch a variety of news clips, which they designed to vary, so that some ended with jokes and others did not. In addition to collecting data on participants' brain activity using fMRI technology, the researchers administered a memory test to determine how much information participants retained from watching the clips. The researchers also asked participants to answer questions about how likely they would be to share the news clips with others.

Participants were more likely to remember information about politics and government policy when it was conveyed in a humorous rather than non-humorous manner and were more willing to share the information online. The findings also show that humorous news clips elicited greater activity in brain regions associated with thinking about what other people think and feel, which highlights the social nature of comedy.

Read more at Science Daily

What happens when your brain can't tell which way is up or down?

 What feels like up may actually be some other direction depending on how our brains process our orientation, according to psychology researchers at York University's Faculty of Health.

In a new study published in PLoS One, researchers at York University's Centre for Vision Research found that an individual's interpretation of the direction of gravity can be altered by how their brain responds to visual information. Laurence Harris, a professor in the Department of Psychology in the Faculty of Health and Meaghan McManus, a graduate student in his lab, found, using virtual reality, that people differ in how much they are influenced by their visual environment.

Harris and McManus say that this difference can help us better understand how individuals use visual information to interpret their environment and how they respond when performing other tasks.

"These findings may also help us to better understand and predict why astronauts may misestimate how far they have moved in a given situation, especially in the microgravity of space," says Harris.

In this virtual-reality-based study, McManus and Harris had their participants lie down in a virtual environment that was tilted so that the visual "up" was above their head and not aligned with gravity. They found that the participants could be divided into two groups: one group who perceived they were standing up vertically (aligned with the visual scene) even though they were actually lying down, and a second group who maintained a more realistic idea of their lying position.

The researchers called the first group, "Visual Reorientation Illusion vulnerable" (VRI-vulnerable). The two groups of participants, while in the same physical orientation and seeing the same scene, experienced simulated self-motion through the environment differently. Those that were VRI-vulnerable reported feeling that they were moving faster and further than those that were not. "Not only did the VRI-vulnerable group rely more on vision to tell them how they were oriented, but they also found visual motion to be more powerful in evoking the sensation of moving through the scene," added Harris.

"On Earth, the brain has to constantly decide whether a given acceleration is due to a person's movements or to gravity. This decision is helped by the fact that we normally move at right angles to gravity. But if a person's perception of gravity is altered by the visual environment or by removing gravity, this distinction becomes much harder."

Read more at Science Daily

How medical schools can transform curriculums to undo racial biases

 Medical school curriculums may misuse race and play a role in perpetuating physician bias, a team led by Penn Medicine researchers found in an analysis of curriculum from the preclinical phase of medical education. In a perspective piece published Tuesday in the New England Journal of Medicine, the researchers identified five key categories in which curriculum misrepresented race in class discussions, presentations, and assessments. The authors recommend that rather than oversimplifying conversations about how race affects diseases' prevalence, diagnosis, and treatment, medical school faculty must widen the lens to "impart an adequate and accurate understanding of the complexity of these relationships."

"In medical school, 20 years ago, we often learned that higher rates of hypertension in certain racial and ethnic groups, was due to genetic predisposition, personal behaviors, or unfortunate circumstances. Now we know this is not true. There are no characteristics innate to racial and ethnic groups, biological or otherwise, that adequately explains these differences. They stem, instead, from differential experiences in our society -- it's structural racism, not race," said the study's senior author Jaya Aysola, MD, MPH, assistant dean of Inclusion and Diversity in the Perelman School of Medicine and executive director at the Penn Medicine Center for Health Equity Advancement. "When we speak of dismantling structural racism, we must begin with medical education, where these sorts of race-based biases are still being reinforced in the classroom."

Though the researchers focused on lectures from a single medical school, the study authors from other institutions found similar misrepresentations of race in their preclinical medical curriculums. The five categories of biases that the research team identified were: semantics, prevalence of disparities without context, race-based diagnostic bias, pathologizing race, and race-based clinical guidelines.

For example, the study authors noted the use of "African American," is a socially and politically meaningful identity for many people, but not for all people of African descent. Moreover, they write, it is a poor proxy for genetic difference, since it lumps people from many different ancestral populations together. The researchers also found that students were taught about the disproportionate burden of type 2 diabetes among the U.S. Akimel O'odham (formerly known as Pima) people, without sufficient historical and social context. Despite high degrees of genetic similarity, the Akimel O'odham living in Mexico have significantly lower rates of diabetes and obesity than those living in the U.S. The authors explain that a the construction of the Hoover Dam in 1930 that pushed the Akimel O'odham from their lands and into poverty, not a genetic predisposition, explains this pattern. The researchers also highlighted the teaching of guidelines that endorse the use of racial categories in the diagnosis and treatment of diseases. One course they analyzed, for instance, encouraged the use of race-adjusted glomerular filtration rate, or GFR, equations, which many experts now say limits care for Black patients and exacerbates health disparities.

"Race is not a biomedical term, and it is a poor proxy for ancestry. Yet, we continue to generate, impart, and assess medical knowledge with this imprecision. In doing so, we perpetuate biases and ignore the actual contributors to the race-based differences we see," Aysola said. "There are several aspects of the medical education apparatus that we have to fundamentally change in order to get to the ideal state where we're dismantling the structures that perpetuate racism."

Read more at Science Daily

How Earth's oddest mammal got to be so bizarre

 Often considered the world's oddest mammal, Australia's beaver-like, duck-billed platypus exhibits an array of bizarre characteristics: it lays eggs instead of giving birth to live babies, sweats milk, has venomous spurs and is even equipped with 10 sex chromosomes. Now, an international team of researchers led by University of Copenhagen has conducted a unique mapping of the platypus genome and found answers regarding the origins of a few of its stranger features.

It lays eggs, but nurses, it is toothless, has a venomous spur, has webbed feet, fur that glows and has 10 sex chromosomes. Ever since Europeans discovered the platypus in Australia during the late 1700's, the quirky, duck-billed, semiaquatic creature has baffled scientific researchers.

Modern day researchers are still trying to understand how the platypus -- often considered to be the world's oddest mammal -- got to be so unique. Their understandings have now advanced, to a great degree. For the first time, an international team of researchers, led by University of Copenhagen biologists, has mapped a complete platypus genome. The study is published in the scientific journal, Nature.

"The complete genome has provided us with the answers to how a few of the platypus' bizarre features emerged. At the same time, decoding the genome for platypus is important for improving our understanding of how other mammals evolved -- including us humans. It holds the key as to why we and other eutheria mammals evolved to become animals that give birth to live young instead of egg-laying animals," explains Professor Guojie Zhang of the Department of Biology.

The platypus belongs to an ancient group of mammals -- monotremes -- which existed millions of years prior to the emergence of any modern-day mammal.

"Indeed, the platypus belongs to the Mammalia class. But genetically, it is a mixture of mammals, birds and reptiles. It has preserved many of its ancestors' original features -- which probably contribute to its success in adapting to the environment they live in," says Professor Zhang.

Lays eggs, sweats milk and has no teeth

One of the platypus' most unusual characteristics is that, while it lays eggs, it also has mammary glands used to feed its babies, not through nipples, but by milk -- which is sweat from its body.

During our own evolution, we humans lost all three so-called vitellogenin genes, each of which is important for the production of egg yolks. Chickens on the other hand, continue to have all three. The study demonstrates that platypuses still carry one of these three vitellogenin genes, despite having lost the other two roughly 130 million years ago. The platypus continues to lay eggs by virtue of this one remaining gene. This is probably because it is not as dependent on creating yolk proteins as birds and reptiles are, as platypuses produce milk for their young.

In all other mammals, vitellogenin genes have been replaced with casein genes, which are responsible for our ability to produce casein protein, a major component in mammalian milk. The new research demonstrates that the platypus carries casein genes as well, and that the composition of their milk is thereby quite similar to that of cows, humans and other mammals.

"It informs us that milk production in all extant mammal species has been developed through the same set of genes derived from a common ancestor which lived more than 170 million years ago -- alongside the early dinosaurs in the Jurassic period," says Guojie Zhang.

Another trait that makes the platypus so unique is that, unlike the vast majority of mammals, it is toothless. Although this monotremes' nearest ancestors were toothed, the modern platypus is equipped with two horn plates that are used to mash food. The study reveals that the platypus lost its teeth roughly 120 million years ago, when four of the eight genes responsible for tooth development disappeared.

Only animal with 10 sex chromosomes

Yet another platypus oddity investigated by the researchers was how their sex is determined. Both humans and every other mammal on Earth have two sex chromosomes that determine sex -- the X and Y chromosome system in which XX is female and XY is male. The monotremes, however, including our duck-billed friends from Down Under, have 10 sex chromosomes, with five Y and five X chromosomes.

Thanks to the near-complete chromosomal level genomes, researchers can now suggest that these 10 sex chromosomes in the ancestors of the monotremes were organized in a ring form which was later broken away into many small pieces of X and Y chromosomes. At the same time, the genome mapping reveals that the majority of monotreme sex chromosomes have more in common with chickens than with humans. But what it shows, is an evolutionary link between mammals and birds.

Read more at Science Daily

Modern microbes provide window into ancient ocean

 Step into your new, microscopic time machine. Scientists at the University of Colorado Boulder have discovered that a type of single-celled organism living in modern-day oceans may have a lot in common with life forms that existed billions of years ago -- and that fundamentally transformed the planet.

The new research, which will appear Jan. 6 in the journal Science Advances, is the latest to probe the lives of what may be nature's hardest working microbes: cyanobacteria.

These single-celled, photosynthetic organisms, also known as "blue-green algae," can be found in almost any large body of water today. But more than 2 billion years ago, they took on an extra important role in the history of life on Earth: During a period known as the "Great Oxygenation Event," ancient cyanobacteria produced a sudden, and dramatic, surge in oxygen gas.

"We see this total shift in the chemistry of the oceans and the atmosphere, which changed the evolution of life, as well," said study lead author Sarah Hurley, a postdoctoral research associate in the departments of Geological Sciences and Biochemistry. "Today, all higher animals need oxygen to survive."

To date, scientists still don't know what these foundational microbes might have looked like, where they lived or what triggered their transformation of the globe.

But Hurley and her colleagues think they might have gotten closer to an answer by drawing on studies of naturally-occurring and genetically-engineered cyanobacteria. The team reports that these ancient microbes may have floated freely in an open ocean and resembled a modern form of life called beta-cyanobacteria.

Studying them, the researchers said, offers a window into a time when single-celled organisms ruled the Earth.

"This research gave us the unique opportunity to form and test hypotheses of what the ancient Earth might have looked like, and what these ancient organisms could have been," said co-author Jeffrey Cameron, an assistant professor of biochemistry.

Take a breath

You can still make the case that cyanobacteria rule the planet. Hurley noted that these organisms currently produce about a quarter of the oxygen that comes from the world's oceans.

One secret to their success may lie in carboxysomes -- or tiny, protein-lined compartments that float inside all living cyanobacteria. These pockets are critical to the lives of these organisms, allowing them to concentrate molecules of carbon dioxide within their cells.

"Being able to concentrate carbon allows cyanobacteria to live at what are, in the context of Earth's history, really low carbon dioxide concentrations," Hurley said.

Before the Great Oxidation Event, it was a different story. Carbon dioxide levels in the atmosphere may have been as much as 100 times what they are today, and oxygen was almost nonexistent. For that reason, many scientists long assumed that ancient microorganisms didn't need carboxysomes for concentrating carbon dioxide.

"Cyanobacteria have persisted in some form over two billion years of Earth's history," she said. "They could have been really different than today's cyanobacteria."

To find out how similar they were, the researchers cultured jars filled with bright-green cyanobacteria under conditions resembling those on Earth 2 billion years ago.

Hurley explained that different types of cyanobacteria prefer to digest different forms, or "isotopes," of carbon atoms. As a result, when they grow, die and decompose, the organisms leave behind varying chemical signatures in ancient sedimentary rocks.

"We think that cyanobacteria were around billions of years ago," she said. "Now, we can get at what they were doing and where they were living at that time because we have a record of their metabolism."

Resurrecting zombie microbes

In particular, the team studied two different types of cyanobacteria. They included beta-cyanobacteria, which are common in the oceans today. But the researchers also added a new twist to the study. They attempted to bring an ancient cyanobacterium back from the dead. Hurley and her colleagues used genetic engineering to design a special type of microorganism that didn't have any carboxysomes. Think of it like a zombie cyanobacterium.

"We had the ability to do what was essentially a physiological resurrection in the lab," said Boswell Wing, a study coauthor and associate professor of geological sciences.

But when the researchers studied the metabolism of their cultures, they found something surprising: Their zombie cyanobacterium didn't seem to produce a chemical signature that aligned with the carbon isotope signatures that scientists had previously seen in the rock record. In fact, the best fit for those ancient signals were likely beta-cyanobacteria -- still very much alive today.

The team, in other words, appears to have stumbled on a living fossil that was hiding in plain sight. And, they said, it's clear that cyanobacteria living around the time of the Great Oxygenation Event did have a structure akin to a carboxysome. This structure may have helped cells to protect themselves from growing concentrations of oxygen in the air.

"That modern organisms could resemble these ancient cyanobacteria -- that was really counterintuitive," Wing said.

Scientists, they note, now have a much better idea of what ancient cyanobacteria looked like and where they lived. And that means that they can begin running experiments to dig deeper into what life was like in the 2 billion-year-old ocean.

"Here is hard evidence from the geological record and a model organism that can shed new light on life on ancient Earth," Cameron said.

Read more at Science Daily

Climate change caused mangrove collapse in Oman

 Most of the mangrove forests on the coasts of Oman disappeared about 6,000 years ago. Until now, the reason for this was not entirely clear. A current study of the University of Bonn (Germany) now sheds light on this: It indicates that the collapse of coastal ecosystems was caused by climatic changes. In contrast, falling sea level or overuse by humans are not likely to be the reasons. The speed of the mangrove extinction was dramatic: Many of the stocks were irreversibly lost within a few decades. The results are published in the journal Quaternary Research.

Mangroves are trees that occupy a very special ecological niche: They grow in the so-called tidal range, meaning coastal areas that are under water at high tide and dry at low tide. Mangroves like a warm climate; most species do not tolerate sea surface temperatures below 24 °C (75°F). They are tolerant to salt, but only up to a tolerance limit that varies from species to species. "This is why we find them nowadays mostly in regions where enough rain falls to reduce salinization of the soil," explains Valeska Decker of the Institute for Geosciences at the University of Bonn, the lead author of the study.

Fossil finds prove that there used to be many mangrove lagoons on the coast of Oman. However, some 6,000 years ago these suddenly largely vanished - the reasons for this were previously disputed. Over the past few years, Decker traveled several times to the easternmost country of the Arabian Peninsula to pursue this question for her doctoral thesis. With the support of her doctoral supervisor Prof. Gösta Hoffmann, she compiled numerous geochemical, sedimentological and archaeological findings into an overall picture. "From our point of view, everything suggests that the collapse of these ecosystems has climatic reasons," she says.

Low pressure trough shifted to the south

Along the equator there is a low pressure trough, the Intertropical Convergence Zone, which is situated a little further north or south depending on the season. The Indian summer monsoon, for example, is linked to this zone. It is believed that about 10,000 years ago this zone was much further north than today, which meant the monsoon affected large parts of the Arabian Peninsula. Just over 6,000 years ago this low-pressure trough then shifted to the south, but the reason for this and how fast is still not completely clear.

"That this was the case has been well documented for several years," explains Decker. "Our results now indicate that this climate change had two effects: On the one hand, it caused salinization of the soil, which put the mangroves under extreme stress. On the other hand, the vegetation cover in the affected areas decreased in general due to the greater drought." This increased erosion: The wind carried large amounts of the barren soil into the lagoons. These silted up and successively dried up. The whole thing happened surprisingly fast: "The ecosystems probably disappeared within a few decades," stresses Decker. According to previous studies, the environmental changes were gradual. The mangrove ecosystems struggled till a certain threshold was reached and then collapsed within decades. Nowadays, the only mangroves in Oman are those of a particularly robust species and are found only in a few places.

She was able to exclude other possible causes for the disappearance of the mangroves in her study. For example, the researchers found no evidence of a drop in sea level 6,000 years ago that could have triggered the mangrove extinction. "Archaeological findings also speak against a man-made ecological catastrophe," she says. "It is true that there were humans living in the coastal regions who used the mangroves as firewood. However, they were nomads who did not build permanent settlements. This meant that their need for wood was relatively low - low enough to rule out overuse as a cause."

Read more at Science Daily

Remote sensing data sheds light on when and how asteroid Ryugu lost its water

 Last month, Japan's Hayabusa2 mission brought home a cache of rocks collected from a near-Earth asteroid called Ryugu. While analysis of those returned samples is just getting underway, researchers are using data from the spacecraft's other instruments to reveal new details about the asteroid's past.

In a study published in Nature Astronomy, researchers offer an explanation for why Ryugu isn't quite as rich in water-bearing minerals as some other asteroids. The study suggests that the ancient parent body from which Ryugu was formed had likely dried out in some kind of heating event before Ryugu came into being, which left Ryugu itself drier than expected.

"One of the things we're trying to understand is the distribution of water in the early solar system, and how that water may have been delivered to Earth," said Ralph Milliken, a planetary scientist at Brown University and study co-author. "Water-bearing asteroids are thought to have played a role in that, so by studying Ryugu up close and returning samples from it, we can better understand the abundance and history of water-bearing minerals on these kinds of asteroids."

One of the reasons Ryugu was chosen as a destination, Milliken says, is that it belongs to a class of asteroids that are dark in color and suspected to have water-bearing minerals and organic compounds. These types of asteroids are believed to be possible parent bodies for dark, water- and carbon-bearing meteorites found on Earth known as carbonaceous chondrites. Those meteorites have been studied in great detail in laboratories around the world for many decades, but it is not possible to determine with certainty which asteroid a given carbonaceous chondrite meteorite may come from.

The Hayabusa2 mission represents the first time a sample from one of these intriguing asteroids has been directly collected and returned to Earth. But observations of Ryugu made by Hayabusa2 as it flew alongside the asteroid suggest it may not to be as water-rich as scientists originally expected. There are several competing ideas for how and when Ryugu may have lost some of its water.

Ryugu is a rubble pile -- a loose conglomeration of rock held together by gravity. Scientists think these asteroids likely form from debris left over when larger and more solid asteroids are broken apart by a large impact event. So it's possible the water signature seen on Ryugu today is all that remains of a previously more water-rich parent asteroid that dried out due a heating event of some kind. But it could also be that Ryugu dried out after a catastrophic disruption and re-formation as a rubble pile. It's also possible that Ryugu had a few close spins past the sun in its past, which could have heated it up and dried out its surface.

The Hayabusa2 spacecraft had equipment aboard that could help scientists to determine which scenario was more likely. During its rendezvous with Ryugu in 2019, Hayabusa2 fired a small projectile into the asteroid's surface. The impact created a small crater and exposed rock buried in the subsurface. Using a near-infrared spectrometer, which is capable of detecting water-bearing minerals, the researchers could then compare the water content of surface rock with that of the subsurface.

The data showed the subsurface water signature to be quite similar to that of the outermost surface. That finding is consistent with the idea that Ryugu's parent body had dried out, rather than the scenario in which Ryugu's surface was dried out by the sun.

"You'd expect high-temperature heating from the sun to happen mostly at the surface and not penetrate too far into the subsurface," Milliken said. "But what we see is that the surface and subsurface are pretty similar and both are relatively poor in water, which brings us back to the idea that it was Ryugu's parent body that had been altered."

More work needs to be done, however, to confirm the finding, the researchers say. For example, the size of the particles excavated from the subsurface could influence the interpretation of the spectrometer measurements.

"The excavated material may have had a smaller grain size than what's on the surface," said Takahiro Hiroi, a senior research associate at Brown and study co-author. "That grain size effect could make it appear darker and redder than its coarser counterpart on the surface. It's hard to rule out that grain-size effect with remote sensing."

Luckily, the mission isn't limited to studying samples remotely. Since Hayabusa2 successfully returned samples to Earth in December, scientists are about to get a much closer look at Ryugu. Some of those samples may soon be coming to the NASA Reflectance Experiment Laboratory (RELAB) at Brown, which is operated by Hiroi and Milliken.

Read more at Science Daily

On the road to invisible solar panels: How tomorrow's windows will generate electricity

 Five years after the Paris climate agreement, all eyes are on the world's progress on the road to a carbon-free future. A crucial part of this goal involves the energy transition from fossil fuels to renewable sources, such as sun, water, wind and wave energy. Among those, solar energy has always held the highest hope in the scientific community, as the most reliable and abundant energy source on Earth. In recent decades, solar cells have become cheaper, more efficient, and environment friendly. However, current solar cells tend to be opaque, which prevents their wider use and integration into everyday materials, constrained to being lined up on roofs and in remote solar farms.

But what if next-generation solar panels could be integrated to windows, buildings, or even mobile phone screens? That is the hope of Professor Joondong Kim from the Department of Electrical Engineering at Incheon National University, Korea. In a recent study published in Journal of Power Sources, he and his colleagues detail their latest invention: a fully transparent solar cell. "The unique features of transparent photovoltaic cells could have various applications in human technology," says Prof. Kim.

The idea of transparent solar cells is well known, but this novel application where scientists have been able to translate this idea into practice is a crucial new finding. At present, the materials making the solar cell opaque are the semiconductor layers, those responsible for capturing light and translating it into an electrical current. Hence, Prof. Kim and his colleagues looked at two potential semiconductor materials, identified by previous researchers for their desirable properties.

The first is titanium dioxide (TiO2), a well-known semiconductor already widely used to make solar cells. On top of its excellent electrical properties, TiO2 is also an environment-friendly and non-toxic material. This material absorbs UV light (a part of the light spectrum invisible to the naked eye) while letting through most of the visible light range. The second material investigated to make this junction was nickel oxide (NiO), another semiconductor known to have high optical transparency. As nickel is one of the mist abundant elements on Earth, and its oxide can easily be manufactured at low industrial temperatures, NiO is also a great material to make eco-friendly cells.

The solar cell prepared by the researchers was composed of a glass substrate and a metal oxide electrode, on top of which they deposited thin layers of the semiconductors (TiO2 first, then NiO) and a final coating of silver nanowires, acting as the other electrode in the cell. They ran several tests to evaluate the device's absorbance and transmittance of light, as well as its effectiveness as a solar cell.

Their findings were encouraging; with a power conversion efficiency of 2.1%, the cell's performance was quite good, given that it targets only a small part of the light spectrum. The cell was also highly responsive and worked in low light conditions. Furthermore, more than 57% of visible light was transmitted through the cell's layers, giving the cell this transparent aspect. In the final part of their experiment, the researchers demonstrated how their device could be used to power a small motor. "While this innovative solar cell is still very much in its infancy, our results strongly suggest that further improvement is possible for transparent photovoltaics by optimizing the cell's optical and electrical properties," suggests Prof. Kim.

Read more at Science Daily

Protecting the global food supply chain

 As the world grows increasingly globalized, one of the ways that countries have come to rely on one another is through a more intricate and interconnected food supply chain. Food produced in one country is often consumed in another country -- with technological advances allowing food to be shipped between countries that are increasingly distant from one another.

This interconnectedness has its benefits. For instance, if the United States imports food from multiple countries and one of those countries abruptly stops exporting food to the United States, there are still other countries that can be relied on to supply food. But, as the coronavirus COVID-19 global pandemic has made abundantly clear, it also leaves the food supply chain -- all the steps involved in bringing food from farms to people's tables across the world -- exposed to potential shocks to the system.

A new study published in Nature Food led by the University of Delaware's Kyle Davis looked at how to ensure that food supply chains are still able to function under these types of environmental shocks and highlighted key areas where future research should be focused. Co-authors on the study include Shauna Downs, assistant professor at Rutgers University's School of Public Health, and Jessica A. Gephart, assistant professor in the Department of Environmental Science at American University.

Davis said the motivation behind the paper was to understand current knowledge on environmental disruptions in food supply chains and to investigate evidence that disruptions in one step of the food supply chain impact subsequent stages. The steps on the global food supply chain are described in the paper as food production, storage, processing, distribution and trade, retail and consumption.

"Does a disruption in food production get passed through different steps and ultimately impact distribution and trade, all the way down to the consumers?" asked Davis, assistant professor in the Department of Geography and Spatial Sciences in UD's College of Earth, Ocean and Environment and the Department of Plant and Soil Sciences in UD's College of Agriculture and Natural Resources who is also a resident faculty member with UD's Data Science Institute. "If there's a shock to agriculture on the other side of the world, will you see the effects in your grocery store?"

The environmental disruptions covered in the paper include events like floods, droughts, and extreme heat, as well as other phenomena like natural hazards, pests, disease, algal blooms, and coral bleaching.

Davis said that this work is especially timely -- given the unprecedented effects that the COVID-19 pandemic has had on the entire food supply chain -- and highlights the importance of understanding how to make global food supply chains function properly under stress.

"COVID-19 has affected all steps in the supply chain simultaneously, from not having enough seasonal workers to harvest the crops to meat processing plants temporarily closing because workers get sick, to hoarding behaviors and runs on grocery stores," Davis said. "We've also seen many people losing their jobs, and as a result, they may not be able to purchase certain foods anymore."

Researchers have focused on understanding how temperature and precipitation affect staple crops at the production step in the supply chain, Davis said, but how that impacts the rest of the steps in the food supply chain has not been researched thoroughly. Because of this, we don't have a good grasp of how a suite of disruptions on a variety of food items ultimately impact consumption, food security, and nutrition.

To address these gaps in knowledge, the researchers identified key areas for future research: 1) to understand the shape of a supply chain, meaning its relative number of farmers, distributors, retailers and consumers to identify possible vulnerabilities; 2) to evaluate how simultaneous shocks -- such as droughts in two different places -- impact the whole supply chain; and 3) to quantify the ability for substitutions to occur within supply chains, like switching cornmeal for flour if there is a wheat shortage.

Ultimately, Davis said this work can help policy makers and businesses make food systems more capable of predicting and absorbing unprecedented shocks.

Read more at Science Daily

New tool for reconstructing ancient sea ice to study climate change

 Sea ice is a critical indicator of changes in the Earth's climate. A new discovery by Brown University researchers could provide scientists a new way to reconstruct sea ice abundance and distribution information from the ancient past, which could aid in understanding human-induced climate change happening now.

In a study published in Nature Communications, the researchers show that an organic molecule often found in high-latitude ocean sediments, known as tetra-unsaturated alkenone (C37:4), is produced by one or more previously unknown species of ice-dwelling algae. As sea ice concentration ebbs and flows, so do the algae associated with it, as well as the molecules they leave behind.

"We've shown that this molecule is a strong proxy for sea ice concentration," said Karen Wang, a Ph.D. student at Brown and lead author of the research. "Looking at the concentration of this molecule in sediments of different ages could allow us to reconstruct sea ice concentration through time."

Other types of alkenone molecules have been used for years as proxies for sea surface temperature. At different temperatures, algae that live on the sea surface make differing amounts of alkenones known as C37:2 and C37:3. Scientists can use the ratios between those two molecules found in sea sediments to estimate past temperature. C37:4 -- the focus of this new study -- had been long considered a bit of problem for temperature measurements. It turns up in sediments taken from closer to the Arctic, throwing off the C37:2/C37:3 ratios.

"That was mostly what the C37:4 alkenone was known for -- throwing off the temperature ratios," said Yongsong Huang, principal investigator of the National Science Foundation-funded project and a professor in Brown's Department of Earth, Environmental and Planetary Science. "Nobody knew where it came from, or whether it was useful for anything. People had some theories, but no one knew for sure."

To figure it out, the researchers studied sediment and sea water samples containing C37:4 taken from icy spots around the Arctic. They used advanced DNA sequencing techniques to identify the organisms present in the samples. That work yielded previously unknown species of algae from the order Isochrysidales. The researchers then cultured those new species in the lab and showed that they were indeed the ones that produced an exceptionally high abundance of C37:4.

The next step was to see whether the molecules left behind by these ice-dwelling algae could be used as a reliable sea ice proxy. To do that, the researchers looked at concentrations of C37:4 in sediment cores from several spots in the Arctic Ocean near the present-day sea ice margins. In the recent past, sea ice in these spots is known to have been highly sensitive to regional temperature variation. That work found that the highest concentrations of C37:4 occurred when climate was coldest and ice was at its peak. The highest concentrations dated back to the Younger-Dryas, a period of very cold and icy conditions that occurred around 12,000 years ago. When climate was at its warmest and ice ebbed, C37:4 was sparse, the research found.

"The correlations we found with this new proxy were far stronger than other markers people use," said Huang, a research fellow at the Institute at Brown for Environment and Society. "No correlation will be perfect because modeling sea ice is a messy process, but this is probably about as strong as you're going to get."

And this new proxy has some additional advantages over others, the researchers say. One other method for reconstructing sea ice involves looking for fossil remains of another kind of algae called diatoms. But that method becomes less reliable further back in time because fossil molecules can degrade. Molecules like C37:4 tend to be more robustly preserved, making them potentially better for reconstructions over deep time than other methods.

The researchers plan to further research these new algae species to better understand how they become embedded in sea ice, and how they produce this alkenone compound. The algae appear to live in brine bubbles and channels inside sea ice, but it may also bloom just after the ice melts. Understanding those dynamics will help the researchers to better calibrate C37:4 as a sea ice proxy.

Read more at Science Daily

Astronomers agree: Universe is nearly 14 billion years old

 From an observatory high above Chile's Atacama Desert, astronomers have taken a new look at the oldest light in the universe.

Their observations, plus a bit of cosmic geometry, suggest that the universe is 13.77 billion years old -- give or take 40 million years. A Cornell University researcher co-authored one of two papers about the findings, which add a fresh twist to an ongoing debate in the astrophysics community.

The new estimate, using data gathered at the National Science Foundation's Atacama Cosmology Telescope (ACT), matches the one provided by the standard model of the universe, as well as measurements of the same light made by the European Space Agency's Planck satellite, which measured remnants of the Big Bang from 2009 to '13.

The research was published in the Journal of Cosmology and Astroparticle Physics.

The lead author of "The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectra at 98 and 150 GHz" is Steve Choi, NSF Astronomy and Astrophysics Postdoctoral Fellow at the Cornell Center for Astrophysics and Planetary Science, in the College of Arts and Sciences.

In 2019, a research team measuring the movements of galaxies calculated that the universe is hundreds of millions of years younger than the Planck team predicted. That discrepancy suggested a new model for the universe might be needed and sparked concerns that one of the sets of measurements might be incorrect.

"Now we've come up with an answer where Planck and ACT agree," said Simone Aiola, a researcher at the Flatiron Institute's Center for Computational Astrophysics and first author of one of two papers. "It speaks to the fact that these difficult measurements are reliable."

From Science Daily

Scientists discover how mother-of-pearl self-assembles into a perfect structure

 Mollusks build shells to protect their soft tissues from predators. Nacre, also known as the mother of pearl, has an intricate, highly regular structure that makes it an incredibly strong material. Depending on the species, nacres can reach tens of centimeters in length. No matter the size, each nacre is built from materials deposited by a multitude of single cells at multiple different locations at the same time. How exactly this highly periodic and uniform structure emerges from the initial disorder was unknown until now.

Nacre formation starts uncoordinated with the cells depositing the material simultaneously at different locations. Not surprisingly, the early nacre structure is not very regular. At this point, it is full of defects. "In the very beginning, the layered mineral-organic tissue is full of structural faults that propagate through a number of layers like a helix. In fact, they look like a spiral staircase, having either right-handed or left-handed orientation," says Dr. Igor Zlotnikov, research group leader at the B CUBE -- Center for Molecular Bioengineering at TU Dresden. "The role of these defects in forming such a periodic tissue has never been established. On the other hand, the mature nacre is defect-free, with a regular, uniform structure. How could perfection emerge from such disorder?"

The researchers from the Zlotnikov group collaborated with the European Synchrotron Radiation Facility (ESRF) in Grenoble to take a very detailed look at the internal structure of the early and mature nacre. Using synchrotron-based holographic X-ray nano-tomography the researchers could capture the growth of nacre over time. "Nacre is an extremely fine structure, having organic features below 50 nm in size. Beamline ID16A at the ESRF provided us with an unprecedented capability to visualize nacre in three-dimensions," explains Dr. Zlotnikov. "The combination of electron dense and highly periodical inorganic platelets with delicate and slender organic interfaces makes nacre a challenging structure to image. Cryogenic imaging helped us to obtain the resolving power we needed," explains Dr. Pacureanu from the X-ray Nanoprobe group at the ESRF.

The analysis of data was quite a challenge. The researchers developed a segmentation algorithm using neural networks and trained it to separate different layers of nacre. In this way, they were able to follow what happens to the structural defects as nacre grows.

The behavior of structural defects in a growing nacre was surprising. Defects of opposite screw direction were attracted to each other from vast distances. The right-handed and left-handed defects moved through the structure, until they met, and cancelled each other out. These events led to a tissue-wide synchronization. Over time, it allowed the structure to develop into a perfectly regular and defect-free.

Read more at Science Daily

Supercapacitors challenge batteries

 A team working with Roland Fischer, Professor of Inorganic and Metal-Organic Chemistry at the Technical University Munich (TUM) has developed a highly efficient supercapacitor. The basis of the energy storage device is a novel, powerful and also sustainable graphene hybrid material that has comparable performance data to currently utilized batteries.

Usually, energy storage is associated with batteries and accumulators that provide energy for electronic devices. However, in laptops, cameras, cellphones or vehicles, so-called supercapacitors are increasingly installed these days.

Unlike batteries they can quickly store large amounts of energy and put it out just as fast. If, for instance, a train brakes when entering the station, supercapacitors are storing the energy and provide it again when the train needs a lot of energy very quickly while starting up.

However, one problem with supercapacitors to date was their lack of energy density. While lithium accumulators reach an energy density of up to 265 Kilowatt hours (KW/h), supercapacitors thus far have only been delivering a tenth thereof.

Sustainable material provides high performance

The team working with TUM chemist Roland Fischer has now developed a novel, powerful as well as sustainable graphene hybrid material for supercapacitors. It serves as the positive electrode in the energy storage device. The researchers are combining it with a proven negative electrode based on titan and carbon.

The new energy storage device does not only attain an energy density of up to 73 Wh/kg, which is roughly equivalent to the energy density of an nickel metal hydride battery, but also performs much better than most other supercapacitors at a power density of 16 kW/kg. The secret of the new supercapacitor is the combination of different materials -- hence, chemists refer to the supercapacitor as "asymmetrical."

Hybrid materials: Nature is the role model

The researchers are betting on a new strategy to overcome the performance limits of standard materials -- they utilize hybrid materials. "Nature is full of highly complex, evolutionarily optimized hybrid materials -- bones and teeth are examples. Their mechanical properties, such as hardness and elasticity were optimized through the combination of various materials by nature," says Roland Fischer.

The abstract idea of combining basic materials was transferred to supercapacitors by the research team. As a basis, they used the novel positive electrode of the storage unit with chemically modified graphene and combined it with a nano-structured metal organic framework, a so-called MOF.

Powerful and stable

Decisive for the performance of graphene hybrids are on the one hand a large specific surface and controllable pore sizes and on the other hand a high electrical conductivity. "The high performance capabilities of the material is based on the combination of the microporous MOFs with the conductive graphene acid," explains first author Jayaramulu Kolleboyina, a former guest scientist working with Roland Fischer.

A large surface is important for good supercapacitors. It allows for the collection of a respectively large number of charge carriers within the material -- this is the basic principle for the storage of electrical energy.

Through skillful material design, the researchers achieved the feat of linking the graphene acid with the MOFs. The resulting hybrid MOFs have a very large inner surface of up to 900 square meters per gram and are highly performant as positive electrodes in a supercapacitor.

Long stability

However, that is not the only advantage of the new material. To achieve a chemically stable hybrid, one needs strong chemical bonds between the components. The bonds are apparently the same as those between amino acids in proteins, according to Fischer: "In fact, we have connected the graphene acid with a MOF-amino acid, which creates a type of peptide bond."

The stable connection between the nano-structured components has huge advantages in terms of long term stability: The more stable the bonds, the more charging and discharging cycles are possible without significant performance impairment.

For comparison: A classic lithium accumulator has a useful life of around 5,000 cycles. The new cell developed by the TUM researchers retains close to 90 percent capacity even after 10,000 cycles.

International network of experts

Fischer emphasizes how important the unfettered international cooperation the researchers controlled themselves was when it came to the development of the new supercapacitor. Accordingly, Jayaramulu Kolleboyina built the team. He was a guest scientist from India invited by the Alexander von Humboldt Foundation and who by now is the head of the chemistry department at the newly established Indian Institute of Technology in Jammu.

"Our team also networked with electro-chemistry and battery research experts in Barcelona as well as graphene derivate experts from the Czech Republic," reports Fischer. "Furthermore, we have integrated partners from the USA and Australia. This wonderful, international co-operation promises much for the future."

Read more at Science Daily